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linux/drivers/usb/gadget
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Kuen-Han Tsai e584cb58a2 usb: gadget: f_ncm: Fix net_device lifecycle with device_move 
commit ec35c19696 upstream.

The network device outlived its parent gadget device during
disconnection, resulting in dangling sysfs links and null pointer
dereference problems.

A prior attempt to solve this by removing SET_NETDEV_DEV entirely [1]
was reverted due to power management ordering concerns and a NO-CARRIER
regression.

A subsequent attempt to defer net_device allocation to bind [2] broke
1:1 mapping between function instance and network device, making it
impossible for configfs to report the resolved interface name. This
results in a regression where the DHCP server fails on pmOS.

Use device_move to reparent the net_device between the gadget device and
/sys/devices/virtual/ across bind/unbind cycles. This preserves the
network interface across USB reconnection, allowing the DHCP server to
retain their binding.

Introduce gether_attach_gadget()/gether_detach_gadget() helpers and use
__free(detach_gadget) macro to undo attachment on bind failure. The
bind_count ensures device_move executes only on the first bind.

[1] https://lore.kernel.org/lkml/f2a4f9847617a0929d62025748384092e5f35cce.camel@crapouillou.net/
[2] https://lore.kernel.org/linux-usb/795ea759-7eaf-4f78-81f4-01ffbf2d7961@ixit.cz/

Fixes: 40d133d7f5 ("usb: gadget: f_ncm: convert to new function interface with backward compatibility")
Cc: stable <stable@kernel.org>
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://patch.msgid.link/20260309-f-ncm-revert-v2-7-ea2afbc7d9b2@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-03-19 16:08:28 +01:00
..
function usb: gadget: f_ncm: Fix net_device lifecycle with device_move 2026-03-19 16:08:28 +01:00
legacy Revert "usb: legacy: ncm: Fix NPE in gncm_bind" 2026-03-19 16:08:28 +01:00
udc usb: gadget: tegra-xudc: Add handling for BLCG_COREPLL_PWRDN 2026-03-04 07:21:18 -05:00
composite.c usb: gadget : fix use-after-free in composite_dev_cleanup() 2025-07-21 16:32:23 +02:00
config.c usb: gadget: config: Remove unused usb_gadget_config_buf 2025-06-19 12:26:48 +02:00
configfs.c usb: gadget: configfs: Correctly set use_os_string at bind 2025-09-06 15:22:36 +02:00
configfs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
epautoconf.c usb: gadget: epautoconf: Use USB API functions rather than constants 2025-05-21 13:13:22 +02:00
functions.c USB: add SPDX identifiers to all remaining files in drivers/usb/ 2017-11-04 11:48:02 +01:00
Kconfig usb: gadget: midi2: Reverse-select at the right place 2025-01-07 11:42:22 +01:00
Makefile usb: gadget: Makefile: remove ccflags-y 2022-03-18 12:56:08 +01:00
u_f.c usb: gadget: function: move u_f.h to include/linux/usb/func_utils.h 2024-09-03 09:57:08 +02:00
u_os_desc.h move asm/unaligned.h to linux/unaligned.h 2024-10-02 17:23:23 -04:00
usbstring.c drivers/usb/gadget: refactor min with min_t 2024-11-13 15:09:50 +01:00